254  GLYCERINE  A  SUBSTITUTE  FOR  OILS,  ETC.,  IN  OINTMENTS. 
the  few  medical  friends  to  whom  I  have  shown  the  article  are 
prescribing  it.  The  simple  word  "  Plasma"  I  apply  to  the  ex- 
cipient  itself,  and  to  it  may  be  added  the  particular  title  of  any 
special  preparation— as  for  instance,  "Plasma  Hydrargyri," 
the  analogue  of  "  Unguentum  Hydrargyri"  of  the  Pharmaco- 
poeia ;  "  Plasma  Potassii  Iodidi,"  &c.  &c. 
Many  of  these  preparations  are  made  precisely  according  to 
the  instructions  given  for  their  analogous  ointments.    Thus,  by 
simple  mixture  of  the  ingredients,  substituting  the  "Plasma" 
for  the  fats  in  the  Pharmacopoeia  forms,  are  prepared- 
Plasma  Antimonii  Potassio  Tartratis. 
"  Belladonnse. 
"  Conii. 
"       Gallse  Co. 
«      Hydrargyri  Ammonio  Chloridi. 
"       Hydrargyri  Iodidi. 
«       Hydrargyri  Nitrico  Oxidi. 
"  Opii. 
"       Plumbi  Iodidi. 
"  Sulphuris. 
"  Zinci. 
But  some  are  best  made  by  slightly  varying  processes.  Thus, 
Plasma  Cantharidis"  I  prepare  by  evaporating  the  decoction 
of  the  Spanish  flies  to  an  extract,  and  then  mixing  with  the 
Plasma. 
For  "  Plasma  Hydrargyri  "  I  direct  as  follows 
Take  Mercury,  §xij. 
Glycerine,  f^xij. 
Starch,  3xiv. 
Mix  the  starch  with  six  fluid  drachms  of  the  glycerine,  and 
gradually  adding  the  mercury,  stir  till  globules  disappear. 
Then  add  the  rest  of  the  glycerine,  and  heat  to  240°  Fahrenheit, 
contantly  stirring. 
The  "  killing"  of  the  mercury  by  this  method  is  by  no  means 
a  formidable  task. 
For  "  Plasma  Hydrargyri  Nitratis"  I  employ  the  following 
formula,  which  is  by  calculation  the  same  as  for  the  correspond- 
ing ointment,  excepting  the  free  acid  which  the  fresh  ointment 
always  contains :— 
